75 supermarket and food processing giants have warned the government that a ‘hard Brexit’ will put the UK’s food industry at risk in an open letter to Prime Minister Theresa May.

The letter, which calls for tariff-free access to the Single Market and continued access to an overseas workforce, was organised by the NFU. Signatories include major players in food and retail, like Sainsbury’s, Arla and Muller, Cargill, Weetabix and Marks & Spencer. Britain’s food sector is the largest manufacturing industry left in the country in terms of employment, and wields considerable influence, as Defra has announced efforts to ramp up food exports post-Brexit.

The letter states, "For our sector maintaining tariff-free access to the EU single market is a vital priority. It is where 75% of our food exports go, so all our farming and food businesses wish to achieve this outcome.”

Signatories are also seeking assurances that EU citizens already resident in Britain will be allowed to remain after the Brexit negotiations are completed. They said they want the Prime Minister to “Put Britain’s food at the centre of Brexit negotiations.”

Commenting on the letter on Thursday, NFU President Meurig Raymond said, “Brexit creates an enormous opportunity for farming, food production and for Britain. But to deliver this new future, we must secure the best possible access to the Single Market and continued access to a competent and reliable workforce. Getting this right will set the foundations for a successful new British agricultural policy.

“Agriculture is a litmus-test for the Government’s Brexit negotiations. As the sector most heavily impacted by the referendum outcome, if the Government can make British farming a success post-Brexit then it will be the clearest indication that the country can succeed outside Europe.”

In her public speeches on the topic, Theresa May has suggested that she prioritises cracking down on immigration over access to the single market, and EU leaders have stated plainly that Britain can’t expect single market access without making concessions on the free movement of people; this has been the case for Switzerland and Norway, who guarantee free movement as part of their relationship with the bloc.